ElabInElab experiments, so as not to consume an interface.

I actually modified Keith's changes so that we can dynmaically choose
the single or dual model in the NS file (Keith's changes hardwired the
system to only single control network) since the single network model
has the disadvantage of not allowing new nodes to be added to an inner
elab, which would make it impossible to test some things (like the
newnode path!).

To choose the single control network model, place this in your NS file:

	tb-elabinelab-singlenet

other it defaults to the older dual network model.